Outboard propulsion unit power tilt mechanism



Nov. 15, 1966 l. w. NORTH 3,285,221

OUTBOARD PROPULSION UNIT POWER TILT MECHANISM Filed Sept. 14, 1964 5Sheets-Sheet 1 INVENTOR. lRVl/VG W /VORTH BY (/Qndrus f rl r4 for/13315I. W- NORTH Nov. 15, 1966 OUTBOARD PROPULSION UNIT POWER TILT MECHANISMFiled Sept. 14, 1964 5 Sheets-Sheet 2 INENTOR. W A/0RTH 5 f r/1" e Affone s I. W. NORTH Nov. 15, 1966 OUTBOARD PROPULSION UNIT POWER TILTMECHANISM Filed Sept. 14, 1964 5 Sheets-Sheet 3 INVENTOR. lRV/IVG M. AaRTH BY qndrus ff United States Patent M 3,285,221 OUTBOARD PROPULSIONUNIT POWER TILT MECHANISM Irving W. North, Fond du Lac, Wis., assignorto Kiekhaefer Corporation, Fond du Lac, Wis., a corporation of DelawareFiled Sept. 14, 1964, Ser. No. 396,147 11 Claims. (Cl. 115-41) Thisinvention relates to outboard propulsion units for boats and moreparticularly to a power tilt mechanism therefor.

The invention has been applied to outboard propulsion units wherein thedrive unit is pivotally supported from a transom support member upon agenerally horizontal tilt-axis and wherein the drive unit is releasablysecured against tilting to the support member in the normal operatingposition of the drive unit.

According to one phase of the invention, the power tilt mechanismgenerally includes a source of fluid at a given pressure and anextendable cylinder-piston means disposed between the drive unit and itssupport member. The pressure source and cylinder-piston means areconnected by means including pressure boosting means. The pressureboosting means is adapted to initially provide fluid to thecylinder-piston means at a pressure higher than the given pressure toinitially extend the cylinderpiston means with a force adequate to tiltthe drive unit and overcome the releasable securement between the driveunit and the support member. After the releasable securement isovercome, the pressure boosting means is rendered ineffective and isadapted to pass fluid at the given pressure to extend thecylinder-piston means and further tilt the drive unit upon its tiltaxis. The cylinderpiston means is further adapted to damp the angularmomentum of the drive unit upon striking a submerged or floating object.

According to another phase of the invention, the hydraulic power tiltmechanism is disposed between the propulsion unit and its support meansin such a way that the cylinder-piston means are disposed in a verticalplane or planes substantially parallel to the propeller thrust force inall positions of steering. In accomplishing this the support meanscomprises a member mounted upon the boat transom by means providing forangular steering of the member relative to the boat on a substantiallyvertical axis. 7

The drawings furnished herewith illustrate the best mode for carryingout the invention as presently contemplated and set forth hereinafter.

In the drawings:

FIG. 1 is a side elevation of an outboard propulsion unit showing thedrive unit in its normal operating position and releasably secured toits support member and in phantom lines shows the drive unit in a tiltedposition;

FIG. 2 is a detail sectional view showing the power tilt mechanism ofthis invention generally at a time when the drive unit is in the normaloperating position;

FIG. 3 is a view generally similar to that of FIG. 2 and shows the powertilt mechanism at a time when the drive unit is approaching its positionof maximum tilt; and

FIG. 4 is a sectional view showing an alternate cylinder-piston meansfor the power tilt mechanism of this invention.-

Referring to the drawings, the watercraft 1, only partially shown, ispropelled by the outboard drive unit 2.

3,285,221 Patented Nov. 15, 1966 The drive unit 2 is carried upon theboat transom by sup- ,port means wherein the unit is pivotally supportedon a generally horizontal tilt axis 3 by an intermediate member 4 whichis in turn pivotally supported on a generally vertical steering axis 5by the support structure 6 rigidly secured to the transom 7 of thewatercraft.

The thrust of the propeller 8 is transmitted to the intermediate member4 through abutment means in the form of a transversely extending tiltadjustment pin 9 supported in aligned openings 10 in the transverselyspaced flange members 11 extending rearwardly from the intermediatemember generally beneath the tilt axis 3. The tilt adjustment pin 9 isselectively movable for disposition in a corresponding pair of a seriesof aligned openings 10 provided in flange members 11 to establish thedesired operating trim for the drive unit.

A releasable latch assembly 12 is pivotally carried by the drive unit 2at 13 and is spr'mg-biased into engagement with the tilt adjustment pin9. While the latch' hook 14 normally remains in engagement with the tiltadjustment pin 9 during operation of the drive unit, the hook isdisengageable from the pin when a predetermined pressure is exerted onthe hook to permit tilting of the drive unit 2 about the horizontal axis3 as when the unit strikes a submerged or floating obstruction. The hook14 re-engages the pin 9 when the drive unit returns to its normaloperating position after the unit has cleared the obstruction.

According to this invention, power means are provided for driving thedrive unit 2 about the tilt axis 3 from the normal operating position tothe full tilt position or between intermediate positions as desired. Thepower means includes an extendable hydraulic cylinder-piston arrangement15 which is interposed between the drive unit 2 and the intermediatemember 4. The cylinderpiston arrangement 15 serves also to damp theangular momentum imparted to the drive unit 2 upon impact with asubmerged or floating object.

As generally shown in FIG. 1, the end of cylinder 16 is pivotallymounted upon an anchor pin 17 carried rearwardly of the drive shafthousing 18 and above the anticavitation plate 19 of the drive unit 2.The opposite end of the piston rod 20 is supported within bracket means21 pivotal-1y mounted on an outboard extension of the tilt adjustmentpin 9 carried by the intermediate member 4.

The power means for operating the cylinder-piston arrangement 15 to tiltthe drive unit 2 includes the gear pump 22 which is driven by areversible electric motor 23. That which is the suction side of the pump22 when the drive unit 2 is driven upwardly is provided with an adaptor24 which communicates with the oil sump 25 through priming conduit 26.The flow of oil from the sump 25 through conduit 26 is controlled bycheck valve 27 having an upper closure seat 28 and a lower by-pass seat29 selectively engageable by the loose ball 30 in accordance withpressure during operation of the pump.

The adaptor 24 for pump 22 further communicates with the sump 25 throughconduits 31 and 32 having a valve 33 interposed therebetween. Valve 33includes a rotatable cylindrical element 34 having a pair of angularlyspaced diametrically extending through passages 35 and 36 either ofwhich is capable of connecting conduits 31 and 32 to place the adaptor24 in communication with the sump 25. Valve element 34 has anintermediate position wherein the valve element closes off conduits 31and 32 as generally shown in FIG. 2.

That which is the pressure side of pump 22 when the drive unit 2 isdriven upwardly is provided with an adaptor 37 which communicates withthe sump 25 through the priming conduit 38. A check valve 39 similar tovalve 27 is disposed in conduit 38 and has an upper closure seat 40 anda lower by-pass seat 41 selectively engageable by the loose ball 42.

When the pump 22 is not in operation, the valves 27 and 39 freely passpriming fluid from the sump 25 past the corresponding bypass seats 29and 41. When the pump 22 is operated to tilt up the drive unit 2,pressure at the adaptor 37 closes valve 39 by forcing the ball 42against the upper closure seat 40 and suction at the adaptor 24 retainsvalve 27 open by holding the ball 30 against the corresponding lowerbypass seat 29 as generally shown in FIG. 3. When the pump 22 is drivenreversely to thereby alternate the pressure and suction sides of thepump and permit the drive unit 2 to return to the direction of itsnormal operating position, the ball 30 is forced against its closureseat 28 to close the valve 27. In the latter instance the pressure atadaptor 37 normally exceeds the suction pressure of pump 22 as thecylinder-piston assembly 15 contracts and thereby forces the ball 42against its closure seat 40 to also close valve 39 and prevent flow fromsump 25 through conduit 38.

The adaptor 37 for pump 22 also communicates with a pressure booster ormultiplier 43 through conduits 44 and 45 having the valve 46 interposedtherebetween. Valve 46 is similar to valve 33 and includes the rotatablecylindrical element 47. Element 47 has a pair of diametrically extendingthrough passages 48 and 49 which are similarly angularly spaced aspassages 35 and 36 in valve element 34 of valve 33 and are adapted toconnect conduits 44 and 45 to place the adaptor 37 in communication withthe pressure multiplier 43. Like valve element 34, element 47 of valve46 has an intermediate position wherein the valve element closes offconduits 44 and 45.

The rotatable valve elements 34 and 47 are similarly disposed within therespective valves 33 and 46 and are always operable in unison by thecylinder-piston means 50 disposed therebetween. The piston 51 isslidably disposed in the cylinder 52 and is provided with opposed rods53 and 54 which extend through the opposed cylinder chambers 55 and 56and project through the correspond ing ends of the cylinder. Outwardlyof cylinder 52, the respective rods 53 and 54 are provided withcorresponding offset rack portions 57 and 58. The respective rackportions 57 and 58 meshingly engage corresponding pinions 59 and 60drivingly associated with the corresponding rotatable valve elements 34and 47.

When the pump 22 is not operating, the piston 51 is maintained generallycentrally of cylinder 52 by the helical springs 61 and 62 disposedaround the corresponding piston rods 53 and 54 in abutting relationbetween the piston and the corresponding end walls of the cylinderchambers 55 and 56. As generally shown in FIG. 2, with piston 51disposed generally centrally of the cylinder 52, the valve elements 34and 47 of the corresponding valves 33 and 46 are rotated to anintermediate closed position isolating the pump 22 from the sump 25through conduits 31 and 32 and from pressure multiplier 43 respectively.

Cylinder chamber 55 is placed in communication with the adaptor 24 ofpump 22 through conduit 63 and chamber 56 communicates with the adaptor37 through conduit 64. Thus, when the pump 22 is placed in operation,the pressure differential across the pump acts upon and slidablydisplaces the piston 51 Within cylinder 52. Operation of the pump 22 totilt the drive unit 2 upwardly, effects movement of piston 51 tocompress the spring 61 and thereby rotate the valve elements 34 and 47in a counterclockwise direction. As generally shown in FIG. 3, movementof the piston 51 is interrupted by engagement of the shoulder 65 formedby the offset in 4 rod 54 against the end Wall of cylinder 52 at whichpoint the valve passages 35 and 48 of corresponding valves 33 and 46 areproperly aligned to open the hydraulic circuit between the sump 25 andthe pump 22 via conduits 31 and 32 and between the pump and pressuremultiplier 43 respectively. When the pump 22 is reversely driven, thepiston 51 is moved in the opposite direction compressing spring 62 untilmovement is interrupted by shoulder 66 at which point the valve passages36 and 49 are properly aligned within the corresponding valves to openthe corresponding hydraulic circuits providing for reverse flow of thepressure fluid to permit the drive unit 2 to return in the direction ofits normal operating position.

To tilt the drive unit 2 upwardly, an initial pressure considerablyhigher than normal pump pressure is required to disengage thespring-biased latch assembly 12 on the drive unit from the tiltadjustment pin 9. This initial surge of pressure is developed Within thepressure multiplier 43 the head end of which communicates with conduit45 extending from valve 46. Y

The pressure multiplier 43 generally comprises a closed hollowcylindrical member 67 having a cylindrical core or stationary plunger 68extending inwardly and coaxially from the base end thereof. Core 68 isspaced radially from the inner wall of member 67 and the head 69 thereofis spaced axially from the head 70 of the cylindrical member. A plunger71 is slidably disposed in member 67 ahead of the core 68 and is movablebetween the cylinder head 70 and the head 69 of core 68. The plunger 71includes a cylindrical skirt portion 72 which telescopes upon core 68.

The head chamber 73 ahead of plunger 71 communicates with the chamber 74disposed between the plunger and head 69 of core 68 and within theplunger skirt portion 72 through the axial passage 75 in the plunger.Flow in the corresponding direction through plunger passage 75 iscontrolled by the opposed check valves 76 and 77 disposed adjacent thecorresponding ends of the passage. The balls 78 and 79 of the respectivevalves 76 and 77 are constantly biased toward their corresponding seats80 and 81 by the compression spring 82 therebetween.

When head chamber 73 is subjected to pump pressure and passage 75 isclosed initially by check valve 77 and thereafter by check valve 76 dueto the higher pressure in chamber 74, plunger 71 is forced in thedirection of core 6 8 pushing the fluid from chamber 74 through thestepped core passage 83 and into conduit 84 connected to thecylinder-piston assembly 15. In view of the crosssectional areadifferential between the head chamber 73 and chamber 74, the initialpressure coursing passage 83 and conduit 84 is boosted or multiplied inthe ratio of the areas so that the initial extension of thecylinder-piston assembly 15 can effect a release of the spring-biasedlatch assembly 12 from the tilt adjustment pin 9 on the intermediatemember 4.

After the fluid is substantially displaced from chamber 74 by movementof plunger 71 effecting adequate extension of the cylinder-pistonassembly 15 to effect release of the latch assembly 12, the ball 79 ofcheck valve 77 in passage 75 engages with and is retained unseated bypin 85 extending axially from the head 69 of core 68 as generally shownin FIG. 3. Thereafter substantially normal pump pressure opens checkvalve 76 and courses passages 83 and conduit 84 to further extend thecylinderpiston assembly 15 and tilt the drive unit 2 upwardly relativeto the intermediate member 4 as desired.

When the pump 22 is reversely driven to permit return of the drive unit2 in the direction of its normal operating position, the ball 78 ofcheck valve 76 in passage 75 is seated and the plunger 71 returned inthe direction of the cylinder head 70 by the higher pressure in chamber74 due to the contracting cylinder-piston assembly 15. As the plunger 71approaches cylinder head 70, the ball 78 is unseated by the axiallyextending pin 86 projecting from the cylinder head to provide for returnpassage of the fluid to the sump 25 to permit contraction of thecylinder-piston assembly and return of the drive unit 2 in the directionof its normal operating position.

Conduit 84 communicates with the stepped passage 87 in the piston rod 20of the cylinder-piston assembly 15. At least a portion of conduit 84 isflexible to accommodate movements of the cylinder-piston assembly 15along with the drive unit 2 and intermediate member 4 in a generallyhorizontal plane about the steering axis 5. A velocity check valve 88 isdisposed in conduit 84 and comprises a ball 89 biased in the directionof the cylinder-piston assembly 15 by the spring 90. The spring 90normally biases the ball 89 away from its seat 91 and against theperforated retainer 92 and is able to withstand the pressure due 'AtOcontraction of the cylinder-piston assembly 15 to permit passage offluid from the contracting cylinderpiston assembly when the pump 22 isreversely driven.

The piston 93 is mounted on the end of rod 20 within the cylinder 16 andseparates chamber 94 ahead of the piston from the chamber 95 throughwhich the rod extends. A velocity check valve 96 is disposed in passage97 which extends generally axially of the piston 93 and connects chamber94 with the passage 87 in rod 20. Check valve 96 comprises a ball 98biased in the direction of rod passage 87 by the spring 99. The spring99 biases the ball 98 away from its seat 100 and against the open slotretainer 101. Passage 87 in rod 20 also communica-tes with chamber 95behind piston 93 through the opening 102 in the rod.

Chambers 94 and 95 on the respective sides of piston 93 also communicatethrough passage 103 which extends through the piston and is offset fromthe rod 20. A relatively high pressure check valve 104 permits flowthrough passage 103 only from chamber 95 to chamber 94. Flow in thereverse direction is prevented by valve ball 105 being biased againstits seat 106 by the spring washer 107.

In operation and assuming a desire to tilt the drive unit 2 upwardlyabout the tilt axis 3 from its normal operating position with hook 14 oflatch assembly 12 engaged with the tilt adjustment pin 9 of theintermediate member 4, the initial fluid pressure as generated inchamber 74 of the pressure multiplier 43 courses passage 87 in pistonrod 20, passes around the ball 98 of velocity check valve 96 and enterschamber 94. Since the fluid pressure acts on a larger piston area inchamber 94 than in chamber 95 behind the piston, the cylinder 16 isforced rearwardly with respect to the boat transom 7 under the influenceof the boosted pressure a distance sufficient to effect release of thespring-biased latch assembly 12 from the tilt adjustment pin 9 ofintermediate member 4. Thereafter, substantially normal pump pressurecontinues through passage 87 of the piston rod 20 and flows similarly asthe initially boosted pressure past check valve 96 into chamber 94 tofurther extend cylinder 16 as desired.

If so desired, the drive unit 2 may be tilted upwardly about the axis 3to a maximum position as determined by an appropriate stop, not shown.If the pump 22 is thereupon shut oflf, the rotatable elements 34 and 47of valves 33 and 46 respectively return to the intermediate closedposition to lock the fluid in the system and retain the drive unit in asubstantially maximum tilt position. If desired, the pump 22 may bestopped at any lesser tilt position of drive unit 2, and with stoppageof the pump and consequent closure of valves 33 and 46, the drive unitwill be retained in the desired position. With the fluid in the systemlocked, the drive unit may be retained in a given position even asagainst propeller thrust. Thus, the power means of this invention isparticularly useful when navigating water more shallow than required foroperation of the drive unit at normal operating trim.

When it is desired to return the drive unit 2 about its tilt axis 3 tosome lesser tilt position or all the way to its lowermost normaloperating position, reversal of pump 22 imposes a suction pressure onthe system and permits the cylinder-piston assembly 15 to contract asthe drive unit 2 moves downwardly under the influence of gravity. Uponreturn of the -unit 2 to the normal operating position, the latchassembly 12 is automatically reengaged with the tilt adpustment pin 9 ofthe intermediate member 4.

With the drive unit 2 underway, the cylinder-piston assembly 15 furtherserves as means to damp the angular momentum of the unit as when theunit strikes a submerged or floating object and swings upwardly aboutthe tilt axis 3. Regardless of whether the underway drive unit 2 is inthe normal operating position or in some other tilt position, impactwith a submerged or floating object causes a pressure buildup behindpiston 93 in chamber as the cylinder 16 is extended with the swingingdrive unit. The suddenly increased pressure courses opening 102, rodpassage 87 and conduit 84 to close the velocity check valves 96 and 88and trap the fluid in the cylinderpiston assembly 15. The small amountof fluid under high pressure which may initially get past velocity checkvalve 88 is relieved into the sump 25 past the relatively high pressurecheck valve 108 in conduit 109 connecting the sump and pressuremultiplier 43 to protect the parts in the system. As the cylinder 16 isfurther extended with the swinging drive unit, the pressure in chamber95 continues to buildup to dampen and dissipate a large portion of theenergy imparted to the drive unit and upon exceeding the preset pressureof check valve 104 is relieved through passage 103 into chamber 94. Whenthe swinging drive unit returns to its initial position, the pressurefluid in chamber 94 is forced from the chamber through passage 97 pastthe now open velocity check valve 96. The cross-sectional area ofpassage 97 is selected to provide a controlled flow from chamber 94 backto chamber 95 whereby to limit or impede the eflect of propeller thrustas the drive unit reenters the water on the return swing.

According to the embodiment of FIG. 4, the power means for driving thedrive -unit 2 about the tilt axis 3 includes cylinder-piston means inthe form of a pair of telescoping sleeves 110 and 111. The closed end ofouter sleeve 110 is pivotally mounted upon anchor pin 17 carried by thedrive shaft housing 18. The oposite closed end of inner sleeve 111 issupported within bracket means 21 pivotally mounted on an outwardextension of the tilt adjustment pin 9 carried by the intermediatemember 4. The stepped passage 112 extending substantially the length ofinner sleeve 11 communicates with core passage 83 of the pressuremultiplier 43 through conduit 113 at least a portion of which isflexible. A pair of return springs 114 and 115 are disposed one withinthe other within inner sleeve 111 and have one end thereof engaged over.a transverse pin 116 of the inner sleeve while the opposite spring endsare secured to the projection 117 extending inwardly from the end ofouter sleeve 110.

In operation and with the drive unit 2 in the normal operating positionhaving the releasable latch assembly 12 engaged with the tilt adjustmentpin 9 of intermediate member 4, outer sleeve 110 is extended initiallyby the boosted pressure as generated in chamber 74 of multiplier 43 andconducted to sleeve 111 through core passage 83 and conduit 113 to tiltthe unit sufliciently to etfect release of the latch assembly.Thereafter, further extension of the sleeve 110 to tilt the drive unitto the height desired is efifected by substantially normal pumppressure. Upon reversal of pump 22 and the withdrawal of fluid from thesystem, return movement of the drive unit is effected by gravity withassistance from return springs 114 and 115.

I claim:

1. In combination with an outboard propulsion unit pivotally supportedupon a generally horizontal axis from a support member to provide fortilt movement of the unit in a generally vertical plane and said unitbeing releasably secured against tilting to said member in the normaloperating position of the unit, power means to tilt the unit upwardlyabout said axis and comprising extendable cylinder-piston means disposedbetween the drive unit and the support member, a source of fluid at agiven pressure, and means connecting the pressure source and thecylinder-piston means and including pressure boosting means to initiallyprovide fluid to the cylinder-piston means at a pressure higher thansaid given pressure to initially extend the cylinder-piston means with aforce adequate to tilt the drive unit and overcome the releasablesecurement between the drive unit and the support member, and thereaftersaid pressure booster means being rendered ineffective and being adaptedto pass fluid at the given pressure to extend the cylinder-piston meansand further tilt the drive unit.

2. The invention as set forth in claim 1 wherein the means connectingthe pressure source and the cylinderpiston means includes valve meansinterposed between the cylinder-piston means and the pressure boostingmeans, said valve means-being adapted to close in response to pressureemanating within the cylinder-piston means when the latter is extendedto dampen and dissipate energy imparted to the drive unit upon strikinga submerged or floating object.

3. In combination with an outboard propulsion unit pivotally supportedupon a generally horizontal axis from a support member to provide fortilt movement of the unit in a generally vertical plane and said unitbeing releasably secured against tilting to said member in the normaloperating position of the unit, power means to tilt the unit upwardlyabout said axis and comprising extendable cylinder-piston means disposedbetween the drive unit and the support member, pump means to deliverfluid at a given pressure, and a pressure multiplier connectedrespectively to the pump means and the cylinder-piston means, saidpressure multiplier being adapted to initially deliver fluid to thecylinder-piston means at a pressure higher than the given pressuredelivered by the pump means to initially extend the cylinder-pistonmeans with a force adequate to tilt the drive unit and overcome thereleasable securement between the drive unit and the support member, andafter release of the drive unit from the support member said pressuremultiplier being adapted to pass fluid at the given pressure to extendthe cylinderpiston means arid further tilt the drive unit.

4. The invention as set forth in claim 3 wherein means are provided toreturn the drive unit in the direction of its normal operating positionwhen the pump means is reversely driven.

5. The invention as set forth in claim 4 wherein the return meansconstitute spring means within the cylinder-piston means.

6. The invention as set forth in claim 3 wherein the pressure multipliercomprises a pair of telescopingly related plungers having correspondinghead chambers of varying cross-sectional area providing a pressure boostsubstantially in the ratio of the respective areas to initially extendthe cylinder-piston means from the normal operating position of thedrive unit.

7. In a power tilt mechanism for an outboard propulsion unit tiltable ona generally horizontal axis relative to support means for said unit,extendable cylinder-piston means disposed between the unit and thesupport means, pump means to deliver fluid at a given pressure, and apressure multiplier connected respectively to the pump means and thecylinder-piston means, said pressure multiplier comprising a cylindricalhousing having a head end and a base end, a stationary plungerprojecting axially in- Wardly from the base end of said housing andspaced radially from the housing wall, a movable plunger disposedbetween the head end of the housing and the stationary plunger anddefining a head chamber between said movable plunger and the head end ofthe housing communicating with said pump means, said movable plungerincluding skirt means adapted to telescope upon the stationary plungerand to define a pressure chamber between said plungers communicatingwith the cylinderpiston means, passage means in said movable plungerconnecting the head chamber and the pressure chamber, valve means insaid passage means adapted to close in response to said .given pressure,said movable plunger being movable in response to said given pressure tostep up the pressure in the pressure chamber substantially in the ratioof the cross-sectional areas of the respective chambers to initiallydeliver fluid to the cylinder-piston means at a pressure higher thansaid given pressure to tilt the propulsion unit iupwardly a givenamount, and means to open said valve means and pass fluid to thecylinder-piston means at the given pressure to tilt the propulsion unitupwardly beyond said given amount.

8. In a power tilt mechanism for an outboard propulsion unit tiltable ona generally horizontal axis relative to support means for said unit,extendable cylinder-piston means disposed between the unit and thesupport means, first means connected to the cylinder-piston means todeliver fluid at a given pressure, second means connected to thecylinder-piston means to deliver fluid at a pressure higher than saidgiven pressure, said cylinder-piston means initially receiving fluidfrom said second means and being extended at the higher pressure to tiltthe propulsion unit upwardly a given amount and thereafter receivingfluid from said first means and being further extended at the givenpressure to tilt the propulsion unit upwardly beyond said given amount.4

9. The invention as set forth in claim 8 wherein said second pressuremeans is interposed between said first pressure means and thecylinder-piston means.

10. In combination in an outboard propulsion means for boats, supportmeans carried by the boat and steerable relative thereto on asubstantially vertical axis, an outboard propulsion unit carried by saidsupport means and tiltable relative thereto on a substantiallyhorizontal axis, said propulsion unit having underwater propulsion meansexerting a thrust force in the forward direction of said unit,extendable cylinder-piston means disposed between the unit and thesupport means and parallel to said thrust force, means to supplysubstantially incompressible fluid to said cylinder-piston means toactuate the same in a direction to tilt the unit upwardly, means to trapthe fluid in said cylinder-piston means to lock the latter in anyselected position of extension whereby to maintain the propulsion unitin a corresponding tilt position, and means to drain fluid from saidcylinder-piston means to effect a return of said unit to any selectedlower tilt position.

11. In combination in an outboard propulsion means for boats, supportmeans carried by the boat and steerable relative thereto on asubstantially vertical axis, an outboard propulsion unit carried by saidsupport means and tiltable relative thereto on a substantiallyhorizontal axis, said propulsion unit having underwater propulsion meansexerting a thrust force in the forward direction of said unit,extendable cylinder-piston means disposed between the unit and thesupport means and parallel to said thrust force, a source of fluid, pumpmeans, a conduit connecting the pump means with the fluid source and thecylinder-piston means respectively, said pump means being adapted todeliver fluid under pressure to the cylinder-piston means to therebyextend the latter and tilt the propulsion unit relative to the supportmeans, and valve means inerposed in the conduit to control the flow offluid therebetween, said valve means constituting means to trap thefluid in the cylinder-piston means to lock the latter in any desired 910 position of extension whereby to maintain the propulsion 3,024,758 3/1962 Liebef 115-41 unit in a corresponding tilt position. 3,146,755 9/1964 Morse 115-35 3,186,375 1/1965 Cass 11541 References Cited by theExaminer UNITED STATES PATENTS 5 MHJTON BUCHLER, Primary Examiner. 2 7557 195 Wanzer. T. MA] OR, Assistant Examiner.

2,893,342 7/1959 Langford 11541

1. IN COMBINATION WITH AN OUTBOARD PROPULSION UNIT PIVOTALLY SUPPORTEDUPON A GENERALLY HORIZONTAL AXIS FROM A SUPPORT MEMBER TO PROVIDE FORTILT MOVEMENT OF THE UNIT IN A GENERALLY VERTICAL PLANE AND SAID UNITBEING RELEASABLY SECURED AGAINST TILTING TO SAID MEMBER IN THE NORMALOPERATING POSITION OF THE UNIT, POWER MEANS TO TILT THE UNIT UPWARDLYABOUT SAID AXIS AND COMPRISING EXTENDABLE CYLINDER-PISTON MEANS DISPOSEDBETWEEN THE DRIVE UNIT AND THE SUPPORT MEMBER, A SOURCE OF FLUID AT AGIVEN PRESSURE, AND MEANS CONNECTING THE PRESSURE SOURCE AND THECYLINDER-PISTON MEANS AND INCLUDING PRESSURE BOOSTING MEANS TO INITIALLYPROVIDE FLUID TO THE CYLINDER-PISTON MEANS AT A PRESSURE HIGHER THANSAID GIVEN PRESSURE TO INITIALLY EXTEND THE CYLINDER-PISTON MEANS WITH AFORCE ADEQUATE TO TILT THE DRIVE UNIT AND OVERCOME THE